1. Field of the Invention
This invention relates to a facsimile apparatus and in particular to a facsimile apparatus that monitors the use state of an external telephone using a voltage detection circuit incorporated in a semiconductor DAA.
2. Description of the Related Art
In recent years, it is known that a semiconductor data access arrangement (DAA) is used for an interface (I/F) section with a telephone line for the purpose of miniaturizing a facsimile apparatus. A use method of connecting an external telephone to a facsimile apparatus and sharing the same telephone line between the facsimile apparatus and the external telephone is also known. To detect hookup of the external telephone, hitherto, a current detector has been installed between the external telephone and the telephone line. That is, if a DC circuit is closed in conjunction with hookup, a DC loop current flows and thus the current detector is installed between a network and the external telephone to detect the DC loop current and hookup of the external telephone (Refer to JP-A-2003-51926 and US 2003/0048483 A1).
JP-A-2003-51926 (especially [0026]) is referred to as a related art.
The semiconductor DAA used in the I/F section incorporates a voltage detection circuit, and the line voltage when a connection is established, detected by the voltage detection circuit is adjusted so as to become within the range predetermined according to the standard. On the other hand, it is desirable that parts that can be omitted should be omitted as much as possible for miniaturizing the facsimile apparatus and reducing the costs thereof.